The present invention relates to a reel-up in a paper machine in which paper is manufactured in a continuous web reeled onto reeling drums in the reel-up to produce paper reels, the end portions of each reeling drum being provided with a bearing housing and a braking drum with coupling device.
The commonly used reel-up comprises a stand; a driven surface winding means rotatably journalled in the stand over which surface winding means the web runs; two parallel rails mounted in the stand to support the reeling drum at its bearing housing; and a secondary system movable linearly along the rails and provided in the vicinity of each rail with a linearly movable secondary body, actuators for synchronous movement of the secondary bodies, and press devices disposed on the secondary bodies to press against the bearing housings of the reeling drum in order to maintain a predetermined linear pressure in the nip between the surface winding means and the paper reel as it increases in size.
Secondary systems used hitherto do not provide sufficient accuracy in controlling the linear pressure in the nip between the surface winding drum and the paper reel being growing. One type of secondary system comprises pivotable secondary arms having press devices in the form of rotatably journalled rollers, while another type comprises linearly movable secondary carriages supporting stationary press devices. The linear pressure is controlled by moving the reeling drum in relation to the surface winding drum, this being achieved by a corresponding pivoting of the secondary arms and linear movement of secondary carriages, respectively. In secondary systems comprising secondary arms, friction arises in the hydraulic cylinders turning the secondary arms and also in associated connection joints. Furthermore, the measurement result is affected by the unbalanced mass in the parts causing the friction. The roller of each secondary arm presses against the reeling drum at a contact point which describes a downwardly directed, arc shaped path of movement when the secondary arm is turned in order to adjust the reeling drum as the paper reel increases in diameter. Such variation in vertical direction of the contact point for each roller contributes to the linear pressure being uneven during the winding. The use of the linearly movable secondary carriages eliminates the above-mentioned problems with the exception of the problem of friction.
As the demand for greater accuracy in controlling the linear pressure increases, the demand for paper with uniform properties is also increasing. This latter demand applies particularly to soft paper such as tissue and similar paper for sanitary purposes for which uniform density and permeability from the innermost to the outermost layers of the paper reel is of the utmost importance. An attempt to satisfy the demand for a paper with uniform properties a technique has been developed in which the reeling drum is driven centrally.
According to this technique a drive means comprising a rotatable coupling device is used for coaxial connection to a coupling device in the reeling drum. Central driving enables variation of the linear pressure over a larger interval so that compression of the paper web in the nip between the surface winding drum and the paper reel can be reduced. Combination of a linear secondary system with said central driving eliminates the problem of slipping which may occur between the surface winding drum and paper reel, particularly when the size of the paper reel is increased in diameter. Such larger paper reels cannot be achieved using secondary arms since their range is limited, i.e. the finished paper reel cannot be made larger than is permitted by the range of the arms.
Drum reels-up with secondary arms are described, for instance, in the following patent specifications: EP-0 350 212, US-3 743 199, US-3 857 524, US-3 889 892, US-4 778 122, SE-447 816 and SE-461 976. Drum reels-up with linearly movable secondary bodies are described, for instance, in the following patent specifications: DE-1 225 014, US-3 116 031 and US-3 250 483. The central driving is described, for instance, in the following patent specifications: SE-9000538-0, EP-0 330 169 and US-4 179 330.
However, it has not been possible to utilize the advantages of central driving due to difficulties in aligning and coupling together the central driving and the reeling drum during operation. A contributory cause of these difficulties is that the drive means for the central driving is arranged on a special stand at the one side of the drum reel-up and, when in inoperative position, is entirely separated from the secondary system in order to be moved linearly by its own actuator. As will be understood, the special stand with the central drive means also requires a considerable amount of space.
Furthermore, the reeling drum, central drive means and secondary carriage are locked to each other thereby making it impossible to influence the linear pressure by means of a separate arrangement which is separated from the actuators which set the secondary carriages.